The CHM file is preferrably placed on the clients PC (locally). This is due to a Microsoft security measure active since Windows XP SP2. Microsoft released a security patch that makes it impossible to view CHM files that are stored on a network drive (as opposed to CHM files stored on your own computer). The help file will appear, but instead of the topic text you will see an error message "this page cannot be displayed". A list of workarounds that involve changing the registry is given at http://support.microsoft.com/kb/896054. The easiest is to download and run one of the following reg files to make the required registry changes: